Continued investigation showed that the patterns of protein synthesis and ornithine decarboxylase activity in rat adrenal cortex offer hypophysectomy or during regeneration differ from those of RNA and DNA synthesis. These complex patterns do not permit the formulation of a simple hypothesis to explain the trophic action of ACTH. The effects of ACTH, MSH, c-AMP, epinephrine and/or agents disrupting microtubles or microfilaments were examined with several pigment cell types. Some of the results are (1) These agents affect not only pigment organelle movement, but also cause changes in overall cell shape. (2) The same agent may cause opposite effects in two cell types. (3) The movement of carotenoid droplets in goldfish xanthophores is associated with movement of smooth E.R. (4) ACTH treatment of xanthophores causes extensive plasma membrane internalization. (5) The role(s) of microtubles and microfilaments are not understood.